c++ - 错误 C2512 : no appropriate default constructor available (not classes)

Question

我刚开始使用结构，但在动态分配我的结构数组时遇到了问题。我正在做我在书中和互联网上看到的事情，但我做不对。

以下是完整的错误信息:

C2512:“记录”:没有合适的默认构造函数可用

IntelliSense:类“Record”不存在默认构造函数

#include <iostream>
#include <string>
using namespace std;

const int NG = 4; // number of scores

struct Record
{
    string name;  // student name
    int scores[NG];
    double average;

    // Calculate the average
    // when the scores are known
    Record(int s[], double a)
    {
        double sum = 0;

        for(int count = 0; count != NG; count++)
        {
            scores[count] = s[count];
            sum += scores[count];
        }

        average = a;
        average = sum / NG;
    }
};

int main()
{
    // Names of the class
    string names[] = {"Amy Adams", "Bob Barr", "Carla Carr",
                      "Dan Dobbs", "Elena Evans"};

    // exam scores according to each student
    int exams[][NG]= {  {98, 87, 93, 88},
                        {78, 86, 82, 91},
                        {66, 71, 85, 94},
                        {72, 63, 77, 69},
                        {91, 83, 76, 60}};

    Record *room = new Record[5];


    return 0;
}

Answer 1

错误很明显。当您尝试分配数组时:

Record *room = new Record[5];

必须实现默认构造函数，即 Record::Record()，以便可以创建 5 个 Record 实例:

struct Record
{
    ...
    Record() : average(0.0) { }
    Record(int s[], double a) { ... }
};

另请注意，您希望在 C++ 中尽可能避免动态分配(除非您有充分的理由这样做)。在这种情况下，使用 std::vector 会更合理:

std::vector<Record> records(5);